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/*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.auto.value.processor;
import static com.google.auto.common.MoreStreams.toImmutableList;
import static com.google.auto.common.MoreStreams.toImmutableMap;
import static java.lang.Math.min;
import static java.util.stream.Collectors.joining;
import com.google.auto.value.processor.AutoValueishProcessor.Property;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import java.util.stream.IntStream;
import java.util.stream.Stream;
/**
* Code generation to track which properties have been set in a builder.
*
* Every property in an {@code @AutoValue} or {@code @AutoBuilder} builder must be set before the
* {@code build()} method is called, with a few exceptions like {@code @Nullable} and {@code
* Optional} properties. That means we must keep track of which ones have in fact been set. We do
* that in two ways: for reference (non-primitive) types, we use {@code null} to indicate that the
* value has not been set, while for primitive types we use a bitmask where each bit indicates
* whether a certain primitive property has been set.
*
*
Additionally, for Kotlin constructors with default parameters, we track exactly which
* properties have been set so we can invoke the constructor thas has a bitmask indicating the
* properties to be defaulted.
*
*
The public methods in this class are accessed reflectively from the {@code builder.vm}
* template. In that template, {@code $builderRequiredProperties} references an instance of this
* class corresponding to the builder being generated. A reference like {@code
* $builderRequiredProperties.markAsSet($p)} calls the method {@link #markAsSet} with the given
* parameter. A reference like {@code $builderRequiredProperties.requiredProperties} is shorthand
* for {@link #getRequiredProperties() $builderRequiredProperties.getProperties()}.
*/
public abstract class BuilderRequiredProperties {
static final BuilderRequiredProperties EMPTY = of(ImmutableSet.of(), ImmutableSet.of());
// Bitmasks are a bit fiddly because we use them in a couple of ways. The first way is where
// we are just using the bitmasks to track which primitive properties have been set. Then if
// we have three primitive properties we can just check that the bitmask is (1 << 3) - 1, the
// all-ones bitmask, to see that they have all been set. The second way is when we are also
// handling optional Kotlin parameters. Then the bitmasks are different: we have one bit for every
// property, primitive or not, optional or not. To check that the required primitive properties
// have been set, we need to check specific bits. For example if properties 1 and 3 are primitive
// then we need to check (~set$0 & ((1 << 1) | (1 << 3))) == 0. That tests that bits 1 and 3 are
// set, since if either of them is 0 then it will be 1 in ~set$0 and will survive the AND. We can
// also isolate the bits representing optional Kotlin parameters similarly, and pass those to the
// special Kotlin constructor that handles default parameters. Kotlin uses bitmasks for that too:
// they have one bit per parameter, optional or not, but only the bits for optional parameters
// matter. We isolate those bits with `&` operations similar to what was described for primitive
// properties. We also need the all-ones bitmask to implement a "copy constructor" builder, which
// starts out with all properties set.
/** All required properties. */
final ImmutableSet requiredProperties;
/**
* The bit index for each tracked property. Properties are tracked if they are primitive, or if
* this is a Kotlin constructor with default parameters. Non-tracked properties do not appear in
* this map.
*/
final ImmutableMap trackedPropertyToIndex;
/**
* The integer fields that store the bitmask. In the usual case, where there are ≤32 tracked
* properties, we can pack the bitmask into one integer field. Its type is the smallest one that
* fits the required number of bits, for example {@code byte} if there are ≤8 tracked properties.
*
* If there are {@literal >32} tracked properties, we will pack them into as few integer fields
* as possible. For example if there are 75 tracked properties (this can happen) then we will put
* numbers 0 to 31 in an {@code int}, 32 to 63 in a second {@code int}, and 64 to 75 in a {@code
* short}.
*
*
When there are {@literal >32} tracked properties, we could potentially pack them better if
* we used {@code long}. But sometimes AutoValue code gets translated into JavaScript, which
* doesn't handle long values natively. By the time you have that many properties you are probably
* not going to notice the difference between 5 ints or 2 longs plus an int.
*/
final ImmutableList bitmaskFields;
/**
* Represents a field in which we will record which tracked properties from a certain set have
* been given a value.
*/
private static class BitmaskField {
final Class type;
final String name;
/**
* The source representation of the value this field has when all properties have been given a
* value.
*/
final String allSetBitmask;
/**
* The source representation of the value this field has when all required properties have been
* given a value.
*/
final String allRequiredBitmask;
BitmaskField(Class type, String name, String allSetBitmask, String allRequiredBitmask) {
this.type = type;
this.name = name;
this.allSetBitmask = allSetBitmask;
this.allRequiredBitmask = allRequiredBitmask;
}
}
static BuilderRequiredProperties of(
ImmutableSet allProperties, ImmutableSet requiredProperties) {
boolean hasDefaults = allProperties.stream().anyMatch(Property::hasDefault);
return hasDefaults
? new WithDefaults(allProperties, requiredProperties)
: new NoDefaults(requiredProperties);
}
private BuilderRequiredProperties(
ImmutableSet requiredProperties, ImmutableList trackedProperties) {
this.requiredProperties = requiredProperties;
int trackedCount = trackedProperties.size();
this.trackedPropertyToIndex =
IntStream.range(0, trackedCount)
.boxed()
.collect(toImmutableMap(trackedProperties::get, i -> i));
this.bitmaskFields =
IntStream.range(0, (trackedCount + 31) / 32)
.mapToObj(
i -> {
int bitBase = i * 32;
int remainingBits = trackedCount - bitBase;
Class type = classForBits(remainingBits);
String name = "set$" + i;
String allSetBitmask =
(remainingBits >= 32) ? "-1" : hex((1 << remainingBits) - 1);
String allRequiredBitmask =
allRequiredBitmask(trackedProperties, bitBase, remainingBits);
return new BitmaskField(type, name, allSetBitmask, allRequiredBitmask);
})
.collect(toImmutableList());
}
abstract String allRequiredBitmask(
ImmutableList trackedProperties, int bitBase, int remainingBits);
public ImmutableSet getRequiredProperties() {
return requiredProperties;
}
/**
* Returns code to declare any fields needed to track which properties have been set. Each line in
* the returned list should appear on a line of its own.
*/
public ImmutableList getFieldDeclarations() {
return bitmaskFields.stream()
.map(field -> "private " + field.type + " " + field.name + ";")
.collect(toImmutableList());
}
/**
* Returns code to indicate that all tracked properties have received a value. This is needed in
* the {@code toBuilder()} constructor, since it assigns to the corresponding fields directly
* without going through their setters.
*/
public ImmutableList getInitToAllSet() {
return bitmaskFields.stream()
.map(field -> field.name + " = " + cast(field.type, field.allSetBitmask) + ";")
.collect(toImmutableList());
}
/**
* Returns code to indicate that the given property has been set, if assigning to the property
* field is not enough. For reference (non-primitive) properties, assignment is enough, but
* for primitive properties we also need to set a bit in the bitmask.
*/
public String markAsSet(Property p) {
Integer index = trackedPropertyToIndex.get(p);
if (index == null) {
return "";
}
BitmaskField field = bitmaskFields.get(index / 32);
// This use-case is why Java reduces int shift amounts mod 32. :-)
return field.name + " |= " + cast(field.type, hex(1 << index)) + ";";
}
/**
* Returns an expression that is true if the given property is required but has not been set.
* Returns null if the property is not required.
*/
public String missingRequiredProperty(Property p) {
return requiredProperties.contains(p) ? propertyNotSet(p) : null;
}
/**
* Returns an expression that is true if the given property has not been given a value. That's
* only different from {@link #missingRequiredProperty} if the property has a Kotlin default. If
* so, we don't require it to be set at build time (because Kotlin will supply the default), but
* we do require it to be set if it is accessed with a getter on the builder. We don't have access
* to Kotlin parameter defaults so we can't arrange for the builder field to have the same default
* value. Rather than returning a bogus zero value we say the value is unset.
*/
public String noValueToGet(Property p) {
return (requiredProperties.contains(p) || p.hasDefault()) ? propertyNotSet(p) : null;
}
private String propertyNotSet(Property p) {
Integer index = trackedPropertyToIndex.get(p);
if (index == null) {
return "this." + p + " == null";
}
BitmaskField field = bitmaskFields.get(index / 32);
return "(" + field.name + " & " + hex(1 << index) + ") == 0";
}
/**
* Returns an expression that is true if any required properties have not been set. Should not be
* called if there are no required properties.
*/
public abstract String getAnyMissing();
/**
* Returns additional constructor parameters to indicate what properties have been defaulted, or
* an empty string if there are none.
*/
public abstract String getDefaultedBitmaskParameters();
/**
* The smallest primitive integer type that has at least this many bits, or {@code int} if the
* number of bits is more than 32.
*/
private static Class classForBits(int bits) {
return bits <= 8 ? byte.class : bits <= 16 ? short.class : int.class;
}
private static String cast(Class type, String number) {
return (type == int.class) ? number : ("(" + type + ") " + number);
}
@VisibleForTesting
static String hex(int number) {
if (number >= 0) {
if (number < 10) {
return Integer.toHexString(number);
}
if (number <= 0xffff) {
return "0x" + Integer.toHexString(number);
}
}
// It's harder to tell 0x7fffffff from 0x7ffffff than to tell 0x7fff_ffff from 0x7ff_ffff.
String lowNybble = Integer.toHexString(number & 0xffff);
String pad = "000".substring(lowNybble.length() - 1);
return "0x" + Integer.toHexString(number >>> 16) + "_" + pad + lowNybble;
}
/** Subclass for when there are no Kotlin default properties. */
private static final class NoDefaults extends BuilderRequiredProperties {
NoDefaults(ImmutableSet requiredProperties) {
super(requiredProperties, primitivePropertiesIn(requiredProperties));
}
private static ImmutableList primitivePropertiesIn(
ImmutableSet properties) {
return properties.stream().filter(p -> p.getKind().isPrimitive()).collect(toImmutableList());
}
@Override
String allRequiredBitmask(
ImmutableList trackedProperties, int bitBase, int remainingBits) {
// We have to be a bit careful with sign-extension. If we're using a byte and
// the mask is 0xff, then we'll write -1 instead. The comparison set$0 == 0xff
// would always fail since the byte value gets sign-extended to 0xffff_ffff.
// We should also write -1 if this is not the last field.
boolean minusOne = remainingBits >= 32 || remainingBits == 16 || remainingBits == 8;
return minusOne ? "-1" : hex((1 << remainingBits) - 1);
}
/**
* {@inheritDoc}
*
* We check the bitmask for primitive properties, and null checks for non-primitive ones.
*/
@Override
public String getAnyMissing() {
Stream primitiveConditions =
bitmaskFields.stream().map(field -> field.name + " != " + field.allRequiredBitmask);
Stream nonPrimitiveConditions =
requiredProperties.stream()
.filter(p -> !trackedPropertyToIndex.containsKey(p))
.map(this::missingRequiredProperty);
return Stream.concat(primitiveConditions, nonPrimitiveConditions).collect(joining("\n|| "));
}
@Override
public String getDefaultedBitmaskParameters() {
return "";
}
}
/** Subclass for when there are Kotlin default properties. */
private static final class WithDefaults extends BuilderRequiredProperties {
private final ImmutableList allProperties;
WithDefaults(ImmutableSet allProperties, ImmutableSet requiredProperties) {
super(requiredProperties, allProperties.asList());
this.allProperties = allProperties.asList();
}
@Override
String allRequiredBitmask(
ImmutableList trackedProperties, int bitBase, int remainingBits) {
int requiredBits = 0;
for (int bit = 0; bit < remainingBits; bit++) {
Property p = trackedProperties.get(bitBase + bit);
if (requiredProperties.contains(p)) {
requiredBits |= 1 << bit;
}
}
return hex(requiredBits);
}
/**
* {@inheritDoc}
*
* Everything can be checked with bitmask operations. If bit i represents a required
* property then it must be 1 in the bitmask field. So if we invert it we must get 0, and if we
* do that for the field as a whole and AND with a bitmask selecting only required properties we
* should get 0.
*/
@Override
public String getAnyMissing() {
return bitmaskFields.stream()
.filter(field -> !field.allRequiredBitmask.equals("0"))
.map(field -> "(~" + field.name + " & " + field.allRequiredBitmask + ") != 0")
.collect(joining("\n|| "));
}
/**
* {@inheritDoc}
*
*
When there are default parameters, we're calling the special constructor that has one or
* more bitmask parameters at the end. Bit i is set if parameter i (zero-origin)
* has its default value, and then the actual value passed for that parameter is ignored. Our
* bitmask field has a 1 for any parameter that has been set, meaning it has a 0 for any
* parameter that has been defaulted. So we need to invert it, and we also want to AND it with a
* bitmask that selects just the bits for parameters with defaults. (The AND probably isn't
* strictly necessary, since the constructor code doesn't actually look at those other bits, but
* it seems cleaner.) If the bitmask for parameters with defaults is 0 then we can just use 0
* for that bitmask, and if it is ~0 (all 1 bits) then we can skip the AND.
*
*
That special constructor has an additional dummy parameter of type {@code
* DefaultConstructorMarker}. We just pass {@code null} to that parameter.
*/
@Override
public String getDefaultedBitmaskParameters() {
ImmutableList.Builder defaultedBitmasksBuilder = ImmutableList.builder();
for (int bitBase = 0; bitBase < allProperties.size(); bitBase += 32) {
int bitCount = min(32, allProperties.size() - bitBase);
int defaultedBitmask = 0;
for (int i = 0; i < bitCount; i++) {
if (allProperties.get(bitBase + i).hasDefault()) {
defaultedBitmask |= 1 << i;
}
}
defaultedBitmasksBuilder.add(defaultedBitmask);
}
ImmutableList defaultedBitmasks = defaultedBitmasksBuilder.build();
return IntStream.range(0, bitmaskFields.size())
.mapToObj(
i -> {
int defaultedBitmask = defaultedBitmasks.get(i);
switch (defaultedBitmask) {
case 0:
return "0";
case ~0:
return "~" + bitmaskFields.get(i).name;
default:
return "~" + bitmaskFields.get(i).name + " & " + hex(defaultedBitmask);
}
})
.collect(joining(",\n", ",\n", ",\nnull"));
}
}
}